In the furniture industry a piece of upholstered furniture is customarily packaged by heat shrinking a heat shrinkable sheet of plastic onto a piece of furniture. This is usually accomplished by draping a heat shrinkable piece of plastic over the piece of furniture (workpiece) and then conveying the draped workpiece into a furnace where hot air at approximately 375.degree. F. is blown causing the plastic to shrink and take the shape of the outside contour of the workpiece. Known prior art employing this process uses a conveyor to convey draped furniture to a furnace, a conveyor to convey the plastic-draped workpiece through the furnace; and, another conveyor to convey the packaged workpiece (piece of furniture about which plastic has been shrunk) from the furnace to a storage area. Throughout this application, the conveyor that conveys the workpiece to the furnace, the furnace conveyor and the conveyor that conveys packaged workpiece from the furnace will be referred to collectively as the first conveyor.
One of the problems in using this type of prior art apparatus is the distribution of the number of packaged workpieces after they are discharged from the furnace. More often than not, there is a need for a particular packaged workpiece be shunted to a first predetermined area and another following packaged workpiece would need to be shunted to a second predetermined area. There may be a plurality of predetermined areas into which packaged workpieces are sought to be disposed or stored for subsequent shipping.
At first glance, this problem would appear to be easily solved by a combination of photoelectric cells, arms and a number of conveyors disposed at an angle to the first conveyor. It was initially thought that a uniquely marked packaged workpiece could be detected by a light beam from a first photoelectric device thus causing an activation of a second photoelectric device. The interruption of a light path created by this second photoelectric device (transverse to the first conveyor) would cause an arm to be moved to a position transverse to the first conveyor. Such would result in the uniquely marked packaged workpiece being shunted onto another conveyor disposed at an angle to the first conveyor. Non-uniquely marked packaged workpieces would not be detected by the first photoelectric device and thus they would continue to travel in the path of the first conveyor. Once tried, however, this solution failed. Apparently such failure was because the light beam of the first photoelectric device was not sufficiently responsive to the uniquely-marked plastic on the packaged workpieces. Various attempts were made to solve this problem by placing stickers, paint, other indicia on the plastic, all to no avail.
To solve this problem, some method had to be devised to turn on a particular photoelectric device just prior to a given workpiece coming into the juncture of the first conveyor with another conveyor serving a predetermined area. Once turned on, breaking of this light path causes an arm to be moved from a first (non-obstructive) to a second (obstructive) position to shunt the workpiece onto another conveyor. After passage of the workpiece past the light path, the light path is obviously reestablished and such would cause the arm to move from its second to its first position and by so doing turn off the photoelectric device. It is towards the solution of this problem that this invention is directed.